The present invention relates to a mold for producing molded articles such as concrete blocks, more particularly, to such a mold having one or more mold cores which project into the mold cavity for forming depressions on the outer sides of the molded concrete block.
A concrete block produced with such a mold (see for example German patent DE-AS 1 708 675) has on each of its four sides triangular projections and depressions. When the concrete blocks are assembled to form a surface the triangular projections fit into the corresponding recesses of adjacent concrete blocks. The resulting assembly of inter-fitting concrete blocks has high vertical and horizontal load supports on all four sides of the assembled concrete blocks. The triangular shapes of the projections and depressions facilitates interconnecting the concrete blocks when they are being laid.
In order to form the triangular depressions in a concrete block, it is known to move a triangular mold core point first linearly into the mold cavity. The mold wall of the mold is provided with a recess through which the mold core projects into the mold cavity. However, such a structure is disadvantageous since when the mold core is retracted back out of the mold cavity concrete residue remains on the mold core and such residues tend to build up and accumulate over a period of time. As a result, the finished concrete block has an irregular surface and there is a very poor dimensional accuracy of the depressions which makes it very difficult to precisely join the concrete blocks when they are being laid. Also, when the molded block is being removed from the mold and when the mold is being lifted irregularities will occur on the outer sides of the finished concrete block when the mold core is in the withdrawn position and concrete residues will adhere to the mold core. The mold cores must therefore be cleaned at relatively short time intervals and significantly increase the costs of the molding operation.